1. Technical Field
The present disclosure relates to a display device and a method for driving the display device.
2. Description of the Related Art
There has recently been an increasing demand for display devices designed for mobile apparatuses and the like, such as mobile phones and electronic paper. Such display devices include pixels each having a plurality of sub-pixels that output light of respective colors. The display devices switch on and off display on the sub-pixels, thereby causing one pixel to display various colors. Display characteristics, such as resolution and luminance, of the display devices are being improved year by year. An increase in the resolution, however, may possibly reduce an aperture ratio. Accordingly, to achieve higher luminance, it is necessary to increase the luminance of a backlight, resulting in increased power consumption in the backlight. To address this, there has been developed a technology for adding a white pixel serving as a fourth sub-pixel to conventional red, green, and blue sub-pixels (e.g., Japanese Patent Application Laid-open Publication No. 2012-108518 (JP-A-2012-108518)). With this technology, the white pixel increases the luminance, thereby reducing a current value in the backlight and the power consumption. There has also been developed a technology for improving the visibility under external light outdoors with the luminance increased by the white pixel when the current value in the backlight need not be reduced (e.g., Japanese Patent Application Laid-open Publication No. 2012-22217 (JP-A-2012-22217)).
When an image is displayed, a phenomenon called simultaneous contrast may possibly occur. The simultaneous contrast is the following phenomenon: when two colors are displayed side by side in one image, the two colors mutually affect to look contrasted with each other. Let us assume a case where two colors with different hues are displayed in one image, for example. In this case, the hues are recognized in a deviated manner by an observer, whereby one of the colors with a hue having lower luminance may possibly look darker, for example. The technology described in JP-A-2012-22217 derives an extension coefficient (expansion coefficient) for extending (expanding) an input signal based on a gradation value of the input signal. With this technology, the extension coefficient may possibly be fixed in a case where colors have different hues. As a result, the technology described in JP-A-2012-22217, for example, may possibly make the color with a hue having lower luminance look darker because of the simultaneous contrast, thereby deteriorating the image.
For the foregoing reasons, there is a need for a display device that suppresses deterioration in an image and a method for driving the display device.